The Old Post Office is one of the many beautifully designed buildings in Washington, D.C. The structure's tower is run by the National Park Service (NPS), U.S. Dept. of the Interior and open to visitors.
Old Post Office building in Washington, D.C. It's no longer an active Post Office, but houses some offices, businesses and is a historical landmark. Visitors can ride elevators to the top of the tower (run by National Parks Service)